Get more mileage out of being a frequent flier

With airlines raising fares and offering fewer flights, there has never been a better time to take stock of your frequent-flier miles.

Whether by flying or charging your groceries to an airline credit card, racking up frequent-flier miles has never been easier. But keep in mind that they are harder than ever to redeem for flights.

So many people are amassing these "freebies" that there are now an estimated 17 trillion unredeemed miles, or enough for a free airline ticket for every man, woman and child in the U.S. But exchanging them for a free ticket or an upgrade is getting harder, with airlines setting aside fewer seats and adding more blackout dates that limit when you can use the miles to book a flight.

If you want to fly on specific days and times, prepare to use up a lot more miles than the minimum listed by the airlines. And unless they fly every other week, it's unlikely most passengers will be able to accumulate enough miles on one airline to get a free ticket.

"It just seems like it's getting harder and harder to do anything with them," said George Hobica, a travel blogger who recently tried to redeem 25,000 miles on Delta Air Lines to book a round-trip ticket from New York to Boise, Idaho.

But like many travelers these days, Hobica struggled to get a flight. He finally found one, but it entailed flying through Cincinnati and Salt Lake City, adding several hours to the trip. The only other option: Pony up another 25,000 miles for a shorter flight. "These miles just don't go as far as they used to," he said.

What's a traveler to do? Get greedy and find a way to build up those miles, said Randy Petersen, publisher of a Web guide to frequent-flier miles.

Savvy frequent fliers charge almost all of their travel and living expenses on credit cards with airline ties, making sure they pay off the bill each month.

United Airlines' Mileage Plus credit card holders can often get double miles for booking a flight on United with the credit card. They can also get double miles for booking a hotel or renting a car with airline partners. Sometimes the credit card companies will have special promotions offering double miles for buying a book at Barnes & Noble or groceries at Albertsons.

Though programs vary by airline, passengers earn credit for each mile flown and can redeem the "miles" for a free upgrade or flight, typically ranging from 10,000 miles for an upgrade from coach to business class to 25,000 miles for a free round-trip ticket.

One of the more useful tips for most travelers -- even those who aren't flying every other week -- is to concentrate on just one or two programs.

Many travelers sign up for too many, and end up with a spattering of miles across half a dozen programs. Some never build up enough miles, others wait years before reaching the magic number. But by then, the miles may have quietly expired because many programs require a minimum of activity for them to count.

It takes more work, but travelers need to focus on flying with a particular airline, staying at a particular hotel and renting cars from a partner company. If you must book with another airline, check on whether it's part of an alliance.

US Airways, for instance, is a Star Alliance member. So if you are a United Mileage Plus member but have to fly US Air, book the flight through United and you'll get United miles. Some carriers, such as Alaska Airlines, are members of several alliances, which means you can redeem Alaska miles on four of the six biggest U.S. carriers, and vice versa.

Another way to rack up miles quickly is to consider smaller airlines, which sometimes have the best programs. "Bigger is not always better," Petersen says.

Next month, Asiana Airlines, which usually tops surveys for having one of the best programs, will be partnering with Bank of America and American Express to launch a credit card that lets travelers earn triple miles for each dollar spent.

The extra bonus miles would add to the miles the traveler accrues for the flight itself. So an Asiana passenger who purchased a $1,500 round-trip ticket to South Korea with the credit card can rack up more than 16,500 miles with a single trip, or almost half needed to earn a free ticket.

Because Asiana is a Star Alliance member, the miles can be redeemed for free tickets or upgrades on 19 member airlines, such as United, US Air, Lufthansa and Singapore Airlines.

For more detailed guides to frequent-flier programs, consider checking out websites dedicated to the subject.

One of the more useful websites for navigating frequent-flier programs is subscription-based InsideFlyer.com. For an annual online subscription of $12, the website has daily tips and news as well as in-depth reviews of virtually every program available, including those run by airlines, hotels and credit cards.

But if you are an infrequent flier like most of us and don't need a daily guide, consider its free sister site, WebFlyer.com. It offers basic tools for sky warrior wannabes. One cool feature is a listing of bonus promotions such as Alaska Airlines', which will award double miles on all flights until Dec. 31 if you've flown two round trips between Los Angeles and Seattle.

Booking flights and redeeming miles online is also a good way to rack up miles and use fewer to get a free ticket. Many airlines now award bonus miles, sometimes up to 1,000, for booking a flight online. At the same time, it takes fewer miles to get a free ticket or upgrade if done online.

Petersen, who has shared frequent flying tips with celebrities, says some sky warriors use their miles only to upgrade to a better seat.

"Peter Fonda is an upgrade junkie. He uses all his miles for upgrades because he never wants to fly coach," Petersen said, adding that Quincy Jones, on the other hand, uses his miles for free tickets for his family and friends.

"People of all types have figured out there is a way to get something for free," he said.